Calcium carbonate barrier films and uses thereof

ABSTRACT

The present invention provides polyolefin films comprising calcium carbonate that have a reduced moisture vapor transmission rate, methods of making the films, and packaging materials comprising the films.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/086,651, filed Apr. 6, 2009, which is the U.S. National Phase ofPCT/US2006/045179, filed Nov. 20, 2006 and claims the benefit of U.S.Provisional Patent Application No. 60/755,659, filed Dec. 29, 2005, thecontent of which is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention is directed toward a film structure comprising polyolefinand calcium carbonate that has reduced moisture vapor transmission rateand is suitable for packaging moisture-sensitive materials such as dryfoods, animal feed, and pharmaceutical products.

BACKGROUND OF THE INVENTION

Throughout this application various publications are referred to inparenthesis. Full citations for these references may be found at the endof the specification immediately preceding the claims. The disclosuresof these publications are hereby incorporated by reference in theirentireties into the subject application to more fully describe the artto which the subject application pertains.

For packaging of dry foods and other moisture sensitive materials, it isdesirable to have a barrier package that prevents the ingress ofmoisture vapor and thus keeps the contents from becoming soggy. Thepackaging should allow the food material to be containerized into apaperboard box for shelf display and ease of handling.

Polymer films have been developed with the objective of increasing,rather than decreasing, moisture vapor transmission through the film(e.g., PCT International Publication Nos. WO 02/10275 A2, 03/020513 A1and WO 03/031134 A1). In contrast, reduced water vapor transmission rate(WVTR) has been achieved using a laminated paperboard substrate, whichis suitable as a container for beverages (U.S. Patent ApplicationPublication No. 2004/0105942). Reduced WVTRs have also been obtained byorientation of high density polyethylene (HDPE) films (U.S. Pat. Nos.4,183,893, 4,870,122, 6,391,411).

While there are different technologies that provide a moisture vaporbarrier in packaging films, there is a need for improved barrier filmsfor packaging dry foods and other moisture-sensitive material where thefilm is both moisture resistant and economical.

SUMMARY OF THE INVENTION

The present invention satisfies this need by using calcium carbonate(CaCO₃) to provide improved polyolefin barrier films. The barrier filmaffords good moisture vapor resistance, heat sealing and handlingproperties. The barrier structure is comprised of a calcium carbonatecontaining polyolefin film in a single or multiple layer filmconstruction. In structures having a plurality of film barrier layerscomprising CaCO₃, the CaCO₃ provides in each of the multiple barrierlayers a reduced rate of moisture vapor transmission through therespective barrier layers. The films are especially useful in foodpackaging, animal feed packaging, pharmaceutical packaging, andpackaging of other moisture-sensitive materials.

Additional objects of the invention be apparent from the descriptionwhich follows.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to films comprising polyolefin andcalcium carbonate, where the films have a reduced moisture vaportransmission rate (MVTR).

Polyolefins are a family of polymers made from olefin monomers. Examplesinclude polyethylene (PE), polypropylene and polyisoprene. PE can behigh density PE (HDPE, density ≥0.95 gm/cm³), medium density PE (MDPE,density 0.934 to <0.95 gm/cm³) and low density PE (LDPE, density <0.934gm/cm³). LDPE can be linear LDPE (LLDPE). HDPE is a preferredpolyolefin. Medium molecular weight HDPE (MMW-HDPE) is a preferred HDPE.

As used herein, medium molecular weight (MMW) polymers have thefollowing weight distributions: number average molecular weight (Mn) of6,000 to 13,000, weight average molecular weight (Mw) of 50,000 to120,000, and Z average molecular weight (Mz) of 175,000 to 500,000.Preferably, the number average molecular weight (Mn) is 8,000 to 11,000.Preferably, the weight average molecular weight (Mw) is 70,000 to100,000. Preferably, the Z average molecular weight (Mz) is 250,000 to400,000.

A preferred film comprises a) a polyolefin base resin and b) apolyolefin carrier resin admixed with calcium carbonate (CaCO₃), whereinthe CaCO₃ and the carrier resin are present in a ratio of 15/85 to 80/20by weight. Preferably, the base resin and the carrier resin aredifferent resins. The base resin and the carrier resin may differ, forexample, in molecular weight, density, melt index, and/or polydispersityindex. The polydispersity index is the weight average molecular weight(Mw) divided by the number average molecular weight (Mn). The carrierresin may have a Mw/Mn ratio of, e.g., 6.82 and the base resin may havea ratio of e.g., 9.35. The carrier resin and base resin may differ in Zaverage molecular weight (Mz) where, e.g., the carrier resin has a Mz of203,000 and the base resin has a Mz of 332,000.

Another preferred film comprises polyolefin and calcium carbonate(CaCO₃), wherein the film comprises: a) a polyolefin base resin having amelt index of 0.05-2.0 dg/min and a density of 0.958-0.963 g/cm³; b) apolyolefin carrier resin for CaCO₃, wherein the carrier resin has a meltindex of 4-10 dg/min and a density of 0.958-0.963 g/cm³; and c) CaCO₃;wherein CaCO₃ is present in the film in a total concentration of 5%-35%by weight.

An additional preferred film comprises: a) a high density polyethylene(HDPE) base resin, wherein the HDPE base resin has a melt index of0.05-2.0 dg/min and a density of 0.958-0.963 g/cm³; b) a HDPE carrierresin for calcium carbonate (CaCO₃), wherein the HDPE carrier resin hasa melt index of 4-10 dg/min and a density of 0.958-0.963 g/cm³; and c)CaCO₃, wherein the CaCO₃ has a median particle size of 0.7-2.5 μm, a topcut d98 of 4-15 μm, a surface area of 3.3-10.0 m²/g, and a totalconcentration in the film of 5-35% by weight, wherein the CaCO₃ has beentreated with a surface treatment agent at a treatment level of 0.3-2.3%by weight, and wherein the CaCO₃ and the HDPE carrier resin are presentin a ratio of 15/85 to 80/20 by weight. Preferably, the CaCO₃ has beentreated with the surface treatment agent at a treatment level of 1.5-3mg surface treatment agent/m² of CaCO₃. Preferably, the CaCO₃ has beenwet ground and/or dry ground prior to incorporation of CaCO₃ in thefilm. Wet grinding can be carried out in the absence of a grinding aidor in the presence of a grinding aid comprising, e.g., a salt ofpolyacrylic acid and/or a salt of a copolymer of acrylic acid.Preferably, the calcium carbonate is dried after grinding. CaCO₃ can betreated with the surface treatment agent before and/or during and/orafter grinding the CaCO₃.

Another preferred film comprises a) a high density polyethylene (HDPE)having a density of 0.958-0.963 g/cm³, and b) calcium carbonate (CaCO₃)having a median particle size of 0.7-2.5 μm, a top cut d98 of 4-15 μm, asurface area of 3.3-10.0 m²/g, and a total concentration in the film of5-35% by weight.

CaCO₃ and carrier resin can be present in the films in a ratio of 15/85to 80/20 by weight, for example 40/60 to 80/20 by weight. Preferredranges of CaCO₃/carrier resin ratios are 15/85 to less than or equal to(≤) 60/40 by weight, for example 40/60 to 60/40 by weight and 45/55 to55/45 by weight. In a most preferred film, CaCO₃ and carrier resin arepresent in a ratio of 50/50 by weight.

CaCO₃ can be present in the films in a total concentration, for example,of 5%-35% by weight, preferably 20%-30% by weight, and more preferably25% by weight. These concentrations apply both to single layer films andto multi layer films, where some layers may not contain any CaCO₃ orwhere different layers may contain different amounts of CaCO₃.

The base resin of the present invention can have a melt index, forexample, of 0.05-2.0 dg/min, preferably 1 dg/min. The base resin canhave a density of 0.958-0.963 g/cm³, preferably 0.962 g/cm³. Preferably,the base resin is a high density polyethylene (HDPE). Preferably, theHDPE is a medium molecular weight high density polyethylene (MMW-HDPE).Base resins such as MMW-HDPE resins can be produced via Zigler-Nattacatalyst chemistries and generally fall into the range of 0.85 to 1.5dg/min melt index, and densities 0.9580 g/cm³ and higher to the maximumlimits for polyethylene manufactured without co-monomers. A preferredbase resin is a resin having the properties of Resin A (see Table 1,below). In traditional applications, films can be made by extruding thismaterial, or like material in its neat form (without any other additivesor masterbatches). As used herein, this material is referred to as a“base resin.”

The carrier resin for CaCO₃ can have a melt index of 4-10 dg/min,preferably 6.5-8.0 dg/min, and most preferably 6.5 dg/min. The carrierresin can have a density, for example, of 0.958-0.963 g/cm³, preferably0.962 g/cm³. Preferably, the carrier resin is a high densitypolyethylene (HDPE). Preferably, the HDPE is a medium molecular weighthigh density polyethylene (MMW-HDPE).

The CaCO₃ in the films can have a median particle size of 0.7-2.5 μm,preferably 1.4-2.0 μm, and more preferably 1.4 μm. The CaCO₃ can have atop cut d98 of 4-15 μm, preferably 8-10 μm, and more preferably 8 μm.Top cut d98 refers to the average diameter of calcium carbonateparticles in the 98^(th) mass percentile. The CaCO₃ can have a surfacearea of 3.3-10.0 m²/g, preferably 3.3-5.5 m²/g, and more preferably 5.5m²/g.

The calcium carbonate may be a natural ground calcium carbonate such as,for example, ground marble, limestone or chalk, and/or a precipitatedcalcium carbonate (e.g., aragonite, waterite or calcite). Preferably,the calcium carbonate is a natural ground calcium carbonate. Calciumcarbonate can be dry ground and/or wet ground. Wet grinding refers togrinding the calcium carbonate in a liquid medium. Wet grinding may becarried out in the absence of a grinding aid or in the presence of agrinding aid. One or more grinding aid agents can be included, such as,e.g., sodium polyacrylate, a salt of polyacrylic acid, and/or a salt ofa copolymer of acrylic acid. For example, calcium carbonate can bederived from marble, which is finely ground in a high solids aqueousmedia using dispersion aids to keep the particles suspended during theprocess. The material is then dewatered, dried, treated anddeagglomerated to again finely divide the individual particles. Dryingmay take place using any suitable drying equipment and can, for example,include thermal drying and/or drying at reduced pressure using equipmentsuch as an oven, a spray drier (such a spray drier sold by Niro and/orNara), and/or a drying in a vacuum chamber. Drying may be batch wiseand/or continuous.

Surface treatment agents can be added to the CaCO₃ to facilitatedispersion of CaCO₃ in the resin. Surface treatment agents can be, forexample, one or more fatty acids having 8 to 24 carbon atoms. Theseagents include, e.g., one or more of arachidic acid, behenic acid,capric acid, cerotic acid, isostearic acid, lauric acid, myristic acid,montanic acid, palmitic acid and stearic acid. Preferred treatmentagents include stearic acid and a blend of stearic acid and palmiticacid. The fatty acid may be from a vegetable source. The fatty acid maybe kosher. The CaCO₃ can be treated with the surface treatment agent ata treatment level of 0.3-2.3% by weight treatment agent and 97.7-99.7%by weight CaCO₃. Preferably, the treatment level is 0.8-1.1% by weighttreatment agent (89.9%-99.2% by weight CaCO₃), and more preferably 1.1%by weight treatment agent (89.9% by weight CaCO₃). Preferably, thetreatment level is 1.5-3.0 mg of surface treatment agent per m² ofCaCO₃, more preferably 2-2.4 mg agent/m² CaCO₃. For ground CaCO₃, theCaCO₃ can be treated with the surface treatment agent before and/orduring and/or after grinding the CaCO₃.

Construction of moisture vapor barrier packaging films are either monoor multi layer. The present invention is also directed to multilayerfilms that comprise any of the polyolefin and calcium carbonate filmsdisclosed herein, Multi layer films generally use an inner contact layerto promote sealing, where the inner contact layer comprises one or moreof ethylene vinyl acetate (EVA), ethylene ethyl acetate (EEA), andethylene acrylic acid (EAA). Vinyl acetate content in this contact layerresin is typically about 18% by weight. Depending upon the extruderconfiguration in a coextrusion process, there may be anywhere from 2 to7 or more layers.

A preferred multilayer film comprises an inner layer comprising one ormore of ethylene vinyl acetate (EVA), ethylene ethyl acetate (EEA), andethylene acrylic acid (EAA), a core layer comprising polyolefin andcalcium carbonate (CaCO₃), and an outer layer comprising polyolefin andcalcium carbonate (CaCO₃). As used herein, the terms “inner,” “core” and“outer” are used to describe and clarify the relative position ofvarious layers in a multiple layer film construction. The term “inner”refers to the surface of a packaging film that comes in contact with thecontained product; whereas, the term “outer” refers to the outside ofthe packaging film that is in contact with the surrounding atmosphere.“Core” describes the layer effectively sandwiched between the inner andouter layers. The multilayer film can have a weight distribution bylayer, for example, of 25-35% outer layer, 50-60% core layer, and 10-20%inner layer, e.g. 30% outer layer, 55% core layer, and 15% inner layer.

The concentration of ethylene vinyl acetate (EVA), ethylene ethylacetate (EEA), or ethylene acrylic acid (EAA) in the film layercontaining EVA, EEA or EAA can be, for example, 15-20% by weight. Theethylene vinyl acetate (EVA) can have a density, for example, of 0.95g/cm³. The ethylene vinyl acetate (EVA) can have a melt index, forexample, of 1.5 dg/min.

Another multilayer film comprises at least a first layer containing oneor more of ethylene vinyl acetate (EVA), ethylene ethyl acetate (EEA),and ethylene acrylic acid (EAA) and at least a second layer containingpolyolefin and calcium carbonate (CaCO₃), wherein CaCO₃ is present inthe multilayer film in a total concentration of 5%-35% by weight,preferably 20%-30% by weight, and more preferably 25% by weight.

The invention also provides methods of making masterbatch compositionsfor preparing the films, where the methods comprise mixing any of theCaCO₃ and polyolefin carrier resins disclosed herein. By itself, calciumcarbonate is a finely divided powder and can be a difficult to handle,meter and feed to an extrusion system, To facilitate the introduction offinely ground mineral to the extrusion process, a pellet masterbatch canbe produced from select polyolefin (e.g., polyethylene) resin(s) andcalcium carbonate(s). Pellet masterbatches contain calcium carbonate andthe “carrier resin” to bind the pellet. A small amount of antioxidant istypically added to prevent polymer degradation.

A preferred method comprises mixing CaCO₃ with a polyolefin carrierresin, wherein the CaCO₃ and the carrier resin are present in a ratio of15/85 to 80/20 by weight, more preferably 15/85 to 60/40 by weight.Another preferred method comprises mixing CaCO₃ with a HDPE carrierresin, wherein the CaCO₃ and the HDPE carrier resin are present in aratio of 15/85 to 80/20 by weight, more preferably 15/85 to 60/40 byweight. The methods can include forming the masterbatch compositionsinto pellets.

The invention provides masterbatch compositions prepared by any of themethods disclosed herein. A preferred masterbatch composition, forexample, comprises 50% by weight calcium carbonate of 1.4 μm mediandiameter particle size, a top cut particle size d98 of 8.0 μm, with a1.1% by weight stearic acid surface treatment, in a 50% by weight highdensity polyethylene (HDPE) carrier resin of 0.962 g/cm³ density and 6.5dg/min melt index. A treatment level of 1.1% by weight stearic acidmeans 1.1% by weight stearic acid and 98.9% by weight calcium carbonate.

The invention further provides methods of making a film comprisingpolyolefin and calcium carbonate (CaCO₃), wherein the method comprisesblending any of the masterbatch composition disclosed herein with any ofthe polyolefin base resins disclosed herein. The masterbatch compositionand the base resin can each be in the form of pellets, which can beblended in a desired ratio. The blended pellets are melted and thenextruded or stretched into an intermediate film, which can thenstretched to form a final film.

Selection of the carrier resin is critical in determining the resultantphysical properties of the film, especially at higher CaCO₃ loadinglevels. As disclosed in the present invention, it is advantageous to usea carrier resin that is different than the base resin in order to obtaineither better production efficiencies or quality of the masterbatch,and/or desired physical properties of the resultant extrudates.Preferred carrier resins are polyethylenes of higher melt index (lowermolecular weight), which work to improve MVTR barrier properties. Apreferred carrier resin is one having the properties of Resin B (seeTable 1, below).

An alternative to using a pellet masterbatch system to deliver calciumis using a fully formulated resin. In this case, a resin would becompounded with the desired amount of calcium carbonate and pelleted.The pellets would then be directly added to an extruder to produce anextrudate of the desired type.

The film making methods can include coextruding a film layer comprisingpolyolefin and calcium carbonate with a film layer comprising one ormore of ethylene vinyl acetate (EVA), ethylene ethyl acetate (EEA), andethylene acrylic acid (EAA). For example, an inner film layer comprisingone or more of ethylene vinyl acetate (EVA), ethylene ethyl acetate(EEA), and ethylene acrylic acid (EAA) is coextruded with a core filmlayer comprising polyolefin and calcium carbonate (CaCO₃) and an outerfilm layer comprising polyolefin and calcium carbonate (CaCO₃).

Coextrusion as a polymer materials processing technique uses multipleextruders to feed a die block to combine multiple polymer flow streamsprior to shaping the combined melt in a die. The advantage of usingcoextrusion is the ability to form well bonded structures from multiplematerials of varying properties in a single step. The method ofproduction by coextrusion according to this invention may, for example,be carried out by leading two or more kinds of olefin resins,plasticized by means of two or more extruders, into a common die andcausing them to come into contact inside or at the opening of the die tothereby form in the first step a film with two or more layers.

Preferably, the film is processed at a blow up ratio (BUR) of from 1.6:1to 2.2:1, more preferably 1.6:1. Preferably, the film is processed at amil gauge of 2.0-3.0, more preferably 2.0-2.5.

The invention provides films made by any of the methods disclosedherein.

Preferred calcium carbonate polyolefin films of the present inventionhave a reduced moisture vapor transmission rate (MVTR) in comparison tothe film in the absence of CaCO₃. As used herein, moisture vaportransmission rate (MVTR) and water vapor transmission rate (WVTR) areused interchangeably. Preferably, the MVTR is reduced by 10-30% comparedto the MVTR of the film in the absence of CaCO₃. More preferably, theMVTR is reduced by 20-30% compared to the MVTR of the film in theabsence of CaCO₃. Even more preferably, the MVTR is reduced by 25-30%compared to the MVTR of the film in the absence of CaCO₃.

The films can have a moisture vapor transmission rate (MVTR) of, forexample, 0.213-0.230 g water vapor-mil/100 in² of film/day, morepreferably 0.213 g water vapor-mil/100 in² of film/day, at 37.5° C. and100% relative humidity. As used herein for values for MVTR, the term“mil” refers to the thickness of the film, where 1 mil= 1/1,000 of aninch of film thickness.

The invention provides packaging films comprising any of the filmsdisclosed herein. The films are especially useful in food packaging,animal feed packaging, pharmaceutical packaging, and packaging of othermoisture-sensitive materials. The food products can be dry foodproducts, such as cereal or crackers. The reduced MVTR of the filmsdisclosed herein helps prevent the ingress of moisture vapor and thuskeeps the food contents from becoming soggy. The film packaging allowsthe food material to be containerized into a paperboard box for shelfdisplay and ease of handling. The films will enable an extended productshelf life in a cost effective package that meets multiple performanceneeds. The films described herein can serve as free standing films,which are not laminated to a support such as a paperboard substrate orother rigid support.

The present invention is illustrated in the following ExperimentalDetails section, which is set firth to aid in the understanding of theinvention, and should not be construed to limit in any way the scope ofthe invention as defined in the claims that follow thereafter.

EXPERIMENTAL DETAILS Overview

To illustrate the properties of a polyolefin film having a calciumcarbonate additive, a comparative study of an extruded 3 layer MMW-HDPEfilm was compared to that of one with similar construction incorporating20-30% by weight calcium carbonate in the total film construction.Calcium carbonate was contained in only the outer and core layers andnot in the inner layer. The calcium carbonate was incorporated as acalcium carbonate masterbatch.

A three layer film was coextruded using a MMW-HDPE base resin (Resin Ain Table 1) having a density of 0.962 g/cm³ and a 1.0 dg/min melt indexfor the outer and core layers, with an inner layer of ethylene vinylacetate (EVA) (Dupont Evlax® 3169Z) with a density of 0.95 g/cm³, 1.5dg/min melt index and 18% by weight vinyl acetate co-monomer. Thepurpose of the inner EVA layer is to provide enhanced seal performanceby allowing lower seal initiation temperatures, and shorter seal dwelltime in the bag making process.

The coextrusion layer distribution consisted of 30% outer layer, 55%core layer and 15% inner EVA layer by weight. Total mineral load wastargeted at 25% by weight of calcium carbonate in most of the films (seeTable 4, below); therefore, 29.5% by weight calcium carbonate wasnecessary in the outer and core layers to compose the effective amount.Correspondingly, the additive feed system was targeted at 58.8% byweight concentrate masterbatch and 41.2% by weight MMW-HDPE (Resin A inTable 1) for the outer and core layer extruders to obtain the 29.5%necessary in these respective layers to hit the effective amount of 25%by weight in the films.

The resultant films were evaluated for physical performance includingmoisture vapor transmission rate (MVTR) using a Mocon PERMATRAN-W® Model3/33. Comparing standard films without calcium carbonate at 3.0 milgauge extruded at 1.6 blow up ratio against the films extruded at lowergauge (2.5 mils) using 25% by weight calcium carbonate extruded atsimilar blow up ratios, resulted in improvements in MVTR as presentedbelow.

Having calcium carbonate present in the outer film layer contributes toa surface roughening effect, which effectively makes the films easier tohandle in secondary operation bag making equipment, and allows foreasier and improved printability and print register. Also, this surfacemodification by addition of calcium carbonate has been shown to lowerthe coefficient of friction.

While a preferred embodiment is made in reference to a co-extrudedpolyolefin film having about 25% weight loading of calcium carbonate, itis recognized that other relative percentages of calcium carbonate inmonolayer or various multi layer construction forms may be utilized. Byway of example, changing the film construction layer distribution or thelocation of the calcium carbonate (calcium carbonate in the core layeronly) would provide a structure having properties similar to theexemplary embodiment set forth.

Details of Experimental Work

Measurements of melt index, density and molecular weight: Melt index wasmeasured using ASTM standard method D1238-04, Standard Test Method forMelt Flow Rates of Thermoplastics by Extrusion Plastometer. Thisstandard can be found in the Annual Book of ASTM Standards 2005, SectionEight—Plastics Volume 8.01. Density was measured using ASTM standardmethod D1501-03, Standard Test Method for Density of Plastics by theDensity-Gradient Technique. This standard can be found in the AnnualBook of ASTM Standards 2005, Section Eight—Plastics Volume 8.01.Molecular weight was determined using a Waters gel permeationchromatograph. The pump used was a 150C operated at a flow rate of 1.00mL/min on an injection volume of 250 μl at 135° C. The sample wasprepared using 12 mg of polyethylene sample dissolved in 4 mL of1,2,4-Trichlorobenzene. The columns used were Waters Styragel HT3, HT4,HT5 and HT6E. Number average molecular weight (Mn), weight averagemolecular weight (Mw) and Z average molecular weight (Mz) are calculatedas follows.

Number average molecular weight (Mn) is the total weight of all thepolymer molecules in a sample, divided by the total number of polymermolecules in the sample. Mn is mathematically expressed as

${Mn} = \frac{\sum\limits_{i = 1}^{\infty}{MiNi}}{\sum\limits_{i = 1}^{\infty}{Ni}}$where Ni is equivalent to the particular number of molecules at a givenmolecular mass and Mi is mole weight of the respective molecules.

Weight average molecular weight (Mw) is the next higher molecular weightmathematically expressed as

${Mw} = \frac{\sum\limits_{i = 1}^{\infty}{NiMi}^{2}}{\sum\limits_{i = 1}^{\infty}{NiMi}}$where each molecule contributes to Mw in proportion to the square of itsrespective mass.

Z average molecular weight (Mz) is the next higher molecular weight toMw and is mathematically expressed as

${Mw} = \frac{\sum\limits_{i = 1}^{\infty}{NiMi}^{3}}{\sum\limits_{i = 1}^{\infty}{NiMi}^{2}}$where each molecule contributes to Mz in proportion to the cube of itsrespective mass.

Measurement of Moisture Vapor Transmission Rate:

Evaluation of the moisture vapor transmission rate (MVTR) performance ofthe films was made on a Mocon Permatran-W Model 3/33. Samples weretested in accordance with ASTM standard, F1249-05 Standard Test Methodfor Water Vapor Transmission Rate Through Plastic Film and SheetingUsing a Modulated Infrared Sensor, operated at 37.8° C. and 100%relative humidity. This standard can be found in the Annual Book of ASTMStandards 2005, Volume 15.09.

Measurement of Particle Size Distribution:

The evaluation of particle size distribution (PSD) was performed viax-ray sedimentation technique using a Sedigraph 5100, in accordance withISO standards 13317-1 General Principles and Guidelines, and 13317-3X-Ray Gravitational techniques. Measurements using Sedigraph were madein the high speed analysis control mode using long flex life Tygontubing. Sample were prepared in a 0.2% by weight sodiumhexametaphosphate dispersant. A 5.0 gram sample was evaluated at 35° C.using an internal fixed-position X-ray source/detector. Samplestarting/end point diameters measure 50-0.5 μm, respectively.

Equipment:

-   -   Extruder: Battenfeld Gloucester co-ex extrusion, 2″ inside        extruder, 3.5″ core (middle) extruder, and a 2″ outside        extruder.    -   Layer Ratio: A (Inside)—30%, B (Core)—55%, and C (Outside)—15%    -   Screen Pack: 20/80/20 Mesh. Same pack configuration used in all        three extruders    -   Die: 8″ Battenfeld Gloucester w/80 mil die gap    -   Air Ring: Egan Davis-Standard dual-lip

Resins:

TABLE 1 Resins Resin Density MI Mn Mw Mz Resin A 0.962 1.0 8799 82314331501 Resin B 0.962 6.5 Resin C 0.962 8.0 9132 62247 203165 Resin D0.962 8.0 Density in g/cm³, MI = melt index (dg/min), Mn = numberaverage molecular weight, Mw = weight average molecular weight, Mz = zaverage molecular weight

Resin D contains a fluoroelastomer polymer processing aid (a flowpromoter) and showed poor response with respect to MVTR.

Calcium Carbonate Minerals:

TABLE 2 Calcium Carbonate Minerals Median Top Calcium Particle Cut-Surface Carbonate Size d98 Area Treatment (CC) type Description (μm)(μm) (m²/g) Level CCA Finely divided marble 1.4 8 5.5 1.1% Wt. wetground at 70%   2 mg/m² solids in presence of sodium polyacrylatedispersant and dried and surface treated CCB Finely divided marble 2.010 3.3 0.8% Wt. wet ground in absence 2.4 mg/m² of a dispersant at 20%solids and dried and surface treated Top cut d98 refers to the averagediameter of calcium carbonate particles in the 98^(th) mass percentile.Treatment level refers to surface treatment of CaCO₃ with stearicacid/palmitic acid blend.

Process:

-   -   Air Ring: Cooling temperature 52-54° F. with a 3.5 inch pressure        (psig).    -   Frost Line: Height range—18 to 19 inches    -   Output Rate: Constant at 250 #/hr.    -   Conditions: Combinations of Blowup Ratio (BUR) and gauge        (thickness measured in mils)

TABLE 3 Processing Conditions Conditions BUR LAYFLAT Gauge 1 1.60 2.00 22.50 3 2.20 2.00 4 2.50 5 1.60 3.00 6 2.2 3.00 BUR = Blow-Up Ratio.

Samples:

TABLE 4 Samples Target CaCO₃ Masterbatch % by weight Masterbatch RatioSample CaCO₃ in film CaCO₃/Resin Mineral/Resin Control 0 — — Sample A 20CCA/Resin B 50/50 Sample B 25 CCA/Resin B 50/50 Sample C 30 CCA/Resin B50/50 Sample D 25 CCB/Resin C 50/50 Sample E 25 CCA/Resin C 50/50 SampleF 25 CCA/Resin D 60/40 Sample G 25 CCA/Resin B 50/50 Sample H 25CCA/Resin B 75/25 Description of Resin types and Calcium carbonate (CC)types in Masterbatch are found in Tables 1 and 2, respectively.

Trial Notes:

Nine samples including a control and five different calcium carbonatemasterbatches were extruded on a Gloucester Battenfeld coextrusion blownfilm line. Except for samples A and C, each of these samples wasextruded at the four different conditions (2.0 and 2.5 gauge, and 1.6and 2.2 blow up ratio). Samples A & C were processed only at the 2.5 milgauge with the 1.6 and 2.2 blow up ratio, respectively. Conditions 5 and6 (Table 3) were used for the controls only.

Results and Discussion

The evaluation objective was to determine which set of extrusion andcalcium carbonate concentrate material combinations provided the highestresistance to moisture vapor transmission rate. It was demonstrated thata film constructed from Resin A with 25% by weight calcium carbonateincorporated via a 50/50 masterbatch of either Resin B or C (Table 1)with Calcium Carbonate (CC) type A (Table 2) provided the bestimprovements to MVTR when processed at the 1.6 blow up ratio and 2.5 milgauge. Table 5A-C summarizes the film performance, including themoisture vapor transmission rate (MVTR) response. The codes in Table5A-C for the Samples and Process Conditions are found in Tables 3 and 4.

The films described herein provide a cost efficient means, compared forexample to the use of metallized films, of providing films with reducedMVTRs that can be used for packaging moisture-sensitive products such asdry foods.

TABLE 5A Results of Film Performance (continued in Table 5B & 5C) SAMPLE& CaCO₃ Resin CaCO₃ CaCO₃ CaCO₃ Film Gauge PROCESS MB Loading Base (CC)in Film in Film Target Measured Basis Wt CONDITION % Wt for MB Type % Wtby Ash BUR mils mils mils Control 1 0 0.19 1.6 2 2.01 1.46 Control 2 00.16 1.6 2.5 2.63 2.15 Control 3 0 0.15 2.2 2 1.97 1.6 Control 4 0 0.152.2 2.5 2.47 2.11 Control 5 0 0.03 1.6 3 3.11 2.31 Control 6 0 0.12 2.23 3.06 2.54 A 2 50 B CCA 20 20.20 1.6 2.5 2.57 2.67 A 4 50 B CCA 2019.45 2.2 2.5 2.46 2.51 B 1 50 B CCA 25 24.19 1.6 2 1.96 2.11 B 2 50 BCCA 25 23.70 1.6 2.5 2.43 2.77 B 3 50 B CCA 25 25.70 2.2 2 2.03 2.26 B 450 B CCA 25 24.43 2.2 2.5 2.45 2.79 C 2 50 B CCA 30 28.52 1.6 2.5 2.582.87 C 4 50 B CCA 30 28.62 2.2 2.5 2.57 2.78 D 1 50 C CCB 25 26.58 1.6 22.02 2.18 D 2 50 C CCB 25 25.20 1.6 2.5 2.56 2.7 D 3 50 C CCB 25 24.712.2 2 2.03 2.17 D 4 50 C CCB 25 25.64 2.2 2.5 2.53 2.75 E 1 50 C CCA 2523.90 1.6 2 2.04 2.19 E 2 50 C CCA 25 24.23 1.6 2.5 2.57 2.72 E 3 50 CCCA 25 23.83 2.2 2 2.04 2.21 E 4 50 C CCA 25 24.28 2.2 2.5 2.51 2.6 F 160 D CCA 25 21.60 1.6 2 1.99 2.23 F 2 60 D CCA 25 21.78 1.6 2.5 2.54 2.8F 3 60 D CCA 25 26.27 2.2 2 1.97 2.2 F 4 60 D CCA 25 23.98 2.2 2.5 2.462.63 G 1 50 B CCA 25 25.62 1.6 2 1.91 2.23 G 2 50 B CCA 25 27.20 1.6 2.52.4 2.85 G 3 50 B CCA 25 24.70 2.2 2 1.93 2.24 G 4 50 B CCA 25 26.02 2.22.5 2.55 2.86 H 1 75 B CCA 25 22.82 1.6 2 1.97 1.91 H 2 75 B CCA 2526.70 1.6 2.5 2.52 2.83 H 3 75 B CCA 25 25.24 2.2 2 2.07 2.19 H 4 75 BCCA 25 30.25 2.2 2.5 2.54 2.83

TABLE 5B Results of Film Performance (continuation of Table 5A) nMVTREffect of SAMPLE & nMVTR (2) CaCO₃ Effect of BUR PROCESS MVTR MeasuredTarget nMVTR nMVTR CONDITION g/100 in²/d g-mil/100 in²/d g-mil/100 in²/d% Improvement % Improvement Control 1 0.177 0.356 0.354 Control 2 0.1080.284 0.270 Control 3 0.132 0.260 0.264 26.91 Control 4 0.097 0.2400.243 8.45 Control 5 0.094 0.292 0.282 Control 6 0.075 0.230 0.225 A 20.1 0.257 0.250 9.52 A 4 0.092 0.226 0.230 12.97 11.94 B 1 0.135 0.2650.270 25.63 B 2 0.091 0.221 0.228 22.15 B 3 0.107 0.217 0.214 16.4717.91 B 4 0.087 0.213 0.218 18.03 3.61 C 2 0.095 0.245 0.238 13.71 C 40.097 0.249 0.243 4.13 −1.71 D 1 0.123 0.248 0.246 30.16 D 2 0.095 0.2430.238 14.38 D 3 0.115 0.233 0.230 10.23 6.04 D 4 0.092 0.233 0.230 10.494.29 E 1 0.139 0.284 0.278 20.30 E 2 0.096 0.247 0.240 13.14 E 3 0.1180.241 0.236 7.43 15.11 E 4 0.097 0.243 0.243 6.37 1.32 F 1 0.161 0.3200.322 9.94 F 2 0.115 0.292 0.288 −2.84 F 3 0.134 0.264 0.268 −1.52 17.61F 4 0.104 0.256 0.260 1.62 12.41 G 1 0.135 0.258 0.270 27.52 G 2 0.0950.228 0.238 19.73 G 3 0.115 0.222 0.230 14.65 13.92 G 4 0.089 0.2270.223 12.72 0.46 H 1 0.195 0.384 0.390 −7.98 H 2 0.121 0.305 0.303 −7.35H 3 0.129 0.267 0.258 −2.69 30.49 H 4 0.091 0.231 0.228 11.11 24.20

TABLE 5C Results of Film Performance (continuation of Table 5A&5B) 2.5mil CACO₃ Containing HDPE film vs.3.0 HDPE Film Average nMVTR AveragenMVTR SAMPLE&PROCESS nMVTR Improvement Improvement CONDITION %Improvement % Improvement % Improvement Control 1 Control 2 Control 3Control 4 Control 5 Control 6 A 2 11.24 A 4 B 1 23.89 20.57 B 2 24.36 B3 17.25 B 4 7.12 C 2 16.16 8.92 C 4 −8.62 D 1 22.27 16.31 D 2 16.81 D 310.36 D 4 −1.42 E 1 16.72 11.81 E 2 15.61 E 3 6.90 E 4 −6.09 F 1 3.551.80 F 2 0.08 F 3 0.05 F 4 −11.48 G 1 23.63 18.66 G 2 22.01 G 3 13.69 G4 1.11 H 1 −7.66 −1.73 H 2 −4.30 H 3 4.21 H 4 −0.71

Notes to Table 5B: “MVTR” is the raw MVTR. “nMVTR” is the MVTR correctedusing measured gauge. “nMVTR(2)” is the MVTR corrected using targetgauge.

“Effect of CaCO3” shows improvement in MVTR (measured gauge corrected)versus control film at same gauge and film orientation (BUR). “Effect ofBUR” shows improvement in MVTR resulting from BUR at equivalent CaCO₃loading and gauge. Positive numbers indicates an improvement (i.e.,reduced MVTR); negative number indicates a deficiency.

Notes to Table 5C: Comparison in Column 3 is between a 2.5 mil filmcontaining CaCO₃ versus a straight 3.0 mil HDPE at equivalent BUR.“Average nMVTR Improvement” in Column 4 is the average improvement inMVTR of CaCO₃ containing samples versus control at a given BUR. “AveragenMVTR Improvement” in Column 5 is the average improvement in nMVTR ofCaCO₃ containing samples versus the control across both gauges and BURsused. Positive numbers indicates an improvement (i.e., reduced MVTR);negative number indicates a deficiency.

REFERENCES

-   PCT International Publication No, WO 02/10275 A2, published Feb. 7,    2002, Eastman Chemical Company.-   PCT international Publication No. WO 03/020513 A1, published Mar.    13, 2003, Kimberly-Clark Worldwide, Inc.-   PCT International Publication No. WO 03/031134 A1, published Apr.    17, 2003, Imerys Minerals Limited.-   U.S. Patent Application Publication No. 2004/0105942 A1, published    Jun. 3, 2004.-   U.S. Pat. No. 4,183,893, issued Jan. 15, 1980.-   U.S. Pat. No. 4,870,122, issued Sep. 26, 1989,-   U.S. Pat. No. 6,391,411 B1, issued May 21, 2002.

The invention claimed is:
 1. A moisture vapor barrier film comprising:a) a polyolefin base resin comprising a high density polyethylene(HDPE); and b) a polyolefin carrier resin admixed with CaCO₃ that hasbeen treated with a surface treatment agent; wherein the CaCO₃ and thecarrier resin are present in a ratio of 15/85 to 80/20 by weight, theCaCO3 is present in the film in a total concentration of 5%-35% byweight, and the film has a moisture vapor transmission rate (MVTR) of0.213-0.390 g water vapor-mil/100 in² of film/day at 37.5° C. and 100%relative humidity, the carrier resin is a high density polyethylene(HDPE), the surface treatment agent is one or more fatty acids having 8to 24 carbon atoms, the base resin comprises from 29.4% to 60.7% byweight of the moisture vapor barrier film, the carrier resin comprisesfrom 9.8% to 35.3% by weight of the moisture vapor barrier film, thebase resin has a melt index of 0.05-2.0 dg/min and a density of0.958-0.963 g/cm³, and the carrier resin has a melt index of 4-10 dg/minand a density of 0.958-0.963 g/cm³.
 2. The moisture vapor barrier filmof claim 1, wherein the base resin has a density of 0.962 g/cm³.
 3. Themoisture vapor barrier film of claim 2, wherein the base resin and thecarrier resin differ in molecular weight, density, melt index and/orpolydispersity index.
 4. The moisture vapor barrier film of claim 1,wherein the base resin has a melt index of 0.85-1.5 dg/min.
 5. Themoisture vapor barrier film of claim 1, wherein the base resin has amelt index of 1 dg/min and a density of 0.962 g/cm³.
 6. The moisturevapor barrier film of claim 1, wherein the carrier resin has a densityof 0.962 g/cm³.
 7. The moisture vapor barrier film of claim 1, whereinthe carrier resin has a melt index of 6.5-8.0 dg/min.
 8. The moisturevapor barrier film of claim 1, wherein the carrier resin has a meltindex of 6.5 dg/min and a density of 0.962 g/cm³.
 9. The moisture vaporbarrier film of claim 1, wherein the concentration of CaCO3 in the filmis 20-30% by weight.
 10. The moisture vapor barrier film of claim 1,wherein the CaCO₃ and the carrier resin are present in a ratio of 40/60to 80/20 by weight.
 11. The moisture vapor barrier film of claim 1,wherein the CaCO₃ and the carrier resin are present in a ratio of 40/60to 60/40 by weight.
 12. The moisture vapor barrier film of claim 1,wherein the CaCO₃ and the carrier resin are present in a ratio of 45/55to 55/45 by weight.
 13. The moisture vapor barrier film of claim 1,wherein the CaCO₃/carrier resin ratio is 50/50 by weight.
 14. Themoisture vapor barrier film of claim 1, wherein the base resin is amedium molecular weight high density polyethylene (MMW-HDPE).
 15. Themoisture vapor barrier film of claim 1, wherein the base resin is aMMW-HDPE having a melt index of 0.85 to 1.5 dg/min.
 16. The moisturevapor barrier film of claim 1, wherein the carrier resin is a mediummolecular weight high density polyethylene (MMW-HDPE).
 17. The moisturevapor barrier film of claim 1, wherein the carrier resin is MMW-HDPEhaving a density of 0.962 g/cm³.
 18. The moisture vapor barrier film ofclaim 1, wherein the surface treatment agent is one or more selectedfrom the group consisting of arachidic acid, behenic acid, capric acid,cerotic acid, isostearic acid, myristic acid, montanic acid, palmiticacid and stearic acid.
 19. The moisture vapor barrier film of claim 1,wherein the calcium carbonate has a median particle size of 0.7-2.5 μm,a top cut d98 of 4-15 μm, and a surface area of 3.3-10.0 m²/g.
 20. Themoisture vapor barrier film of claim 1, wherein the polyolefin baseresin is a MMW-HDPE; and the polyolefin carrier resin has a melt indexof 6.5-8.0 dg/min.
 21. The moisture vapor barrier film of claim 1,wherein the high density polyethylene (HDPE) base resin is a MMW HDPE;the HDPE carrier resin has a melt index of 6.5-8.0 dg/min; the CaCO₃ hasa median particle size of 0.7-2.5 μm, a top cut d98 of 4-15 μm, asurface area of 3.3-10.0 m²/g, and a total concentration in the film of5-35% by weight, and the CaCO₃ has been treated with a surface treatmentagent at a treatment level of 0.3-2.3% by weight.
 22. The moisture vaporbarrier film of claim 1, wherein the moisture vapor barrier filmcomprises MMW-HDPE and the calcium carbonate (CaCO₃) has a medianparticle size of 0.7-2.5 μm, a top cut d98 of 4-15 μm, and a surfacearea of 3.3-10.0 m²/g.
 23. A package for packing moisture sensitivematerial comprising the moisture vapor barrier film of claim
 1. 24. Amultilayer film comprising a moisture vapor barrier film, wherein themoisture vapor barrier film comprises: a) a polyolefin base resincomprising a high density polyethylene (HDPE); and b) a polyolefincarrier resin admixed with CaCO3 that has been treated with a surfacetreatment agent; wherein the CaCO₃ and the carrier resin are present ina ratio of 15/85 to 80/20 by weight, the CaCO₃ is present in the film ina total concentration of 5%-35% by weight of the moisture vapor barrierfilm, and the moisture vapor barrier film has a moisture vaportransmission rate (MVTR) of 0.213-0.390 g water vapor-mil/100 in² offilm/day at 37.5° C. and 100% relative humidity, the carrier resin is ahigh density polyethylene (HDPE), the surface treatment agent is one ormore fatty acids having 8 to 24 carbon atoms, the base resin comprisesfrom 29.4% to 60.7% by weight of the moisture vapor barrier film, thecarrier resin comprises from 9.8% to 35.3% by weight of the moisturevapor barrier film, the base resin has a melt index of 0.05-2.0 dg/minand a density of 0.958-0.963 g/cm³, and the carrier resin has a meltindex of 4-10 dg/min and a density of 0.958-0.963 g/cm³.
 25. Themultilayer film of claim 24, wherein at least a first layer of themultilayer film comprises one or more of ethylene vinyl acetate (EVA),ethylene ethyl acetate (EEA), and ethylene acrylic acid (EAA), and atleast a second layer of the multilayer film comprises polyolefin andcalcium carbonate (CaCO₃), and wherein CaCO₃ is present in themultilayer film in a total concentration of 5%-35% by weight.
 26. Themultilayer film of claim 25, wherein the first layer does not compriseCaCO₃.
 27. The multilayer film of claim 24, wherein the base resincomprises from 29.4% to 53% by weight of the moisture vapor barrierfilm.
 28. The multilayer film of claim 24, wherein the carrier resincomprises from 23.5% to 35.3% by weight of the moisture vapor barrierfilm.
 29. The multilayer film of claim 24, wherein the CaCO₃ and thecarrier resin are present in a ratio of 45/55 to 55/45 by weight of themoisture vapor barrier film.
 30. The multilayer film of claim 24,wherein the sum of the layers which comprise CaCO₃, comprise from 75% to95% by weight of the multilayer film.
 31. The multilayer film of claim24, wherein the concentration of CaCO₃ in the moisture vapor barrierfilm is 20-30% by weight.
 32. A package for packing moisture sensitivematerial comprising the multilayer film of claim 24.